1. Field of the Invention
The invention relates to a semiconductor device and a manufacturing method of a semiconductor device.
2. Description of the Related Art
A thin film transistor used for a semiconductor device, a display device, or the like is required to have different characteristics depending on the purpose or function of the semiconductor device. It is important to control the characteristics of the thin film transistor to satisfy the requirement, and a technique for manufacturing the thin film transistor has been researched to provide characteristics appropriate for the intended use.
In a thin film transistor, by etching a gate electrode layer into stacked layers of different shapes or a tapered shape and adding impurity elements by utilizing the etched shape, a technique to form impurity regions with different concentrations in a semiconductor layer in a self-aligned manner has been reported (for example, see Patent Document 1).